JPH0794481A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a semiconductor device by which step disconnection of a second layer wiring is reliably prevented by a slight change of the process. CONSTITUTION:A photoresist mask 5 having an opening pattern 6 is provided on an intermediate insulating film composed of a protective film 3 and a polyimid film 4 formed in multilayer from the side of a semiconductor substrate 1 for forming an opening 7 in the polyimide film 4 by etching and an opening 8 is formed in the protective film 3 by etching having the photoresist mask 5 and the polyimide film 4 as masks and the polyimide film 4 is again selectively etched using the photoresist mask 5. Then, the opening 7 of the polyimide film 4 is enlarged relative to the opening 8 of the protective film 3, and an opening to be formed getting together these openings is made into an upwardly opened shape and after removing the photoresist mask 5, a wiring 9 for plating connected to an ohmic electrode 2 provided on the polyimide film 4 is provided in order to reliably prevent step disconnection of the wiring 9 for plating on the way to the opening.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming a multi-layer wiring via an intermediate insulating film.

[0002]

2. Description of the Related Art A gallium arsenide field effect transistor device which exhibits highly efficient performance in a high frequency region has a structure in which a plurality of transistor elements are connected in parallel. Therefore, it is necessary to form a two-layer wiring structure in which an opening is formed in the intermediate insulating film provided on the transistor element by etching and the wiring provided on the intermediate insulating film is connected to the electrode of the transistor element through this opening. There is.

A conventional method for forming a two-layer wiring structure will be described with reference to FIGS. As shown in FIG. 3, a gallium arsenide substrate 1 is preliminarily formed with a transistor element, and is provided with an ohmic electrode 2 which makes ohmic contact with a source or drain region. Then, on the gallium arsenide substrate 1, a silicon nitride film (SiN
3) and a polyimide film 4 are provided, and these films 3, 4 are provided.
The intermediate insulating film for interlayer insulation is constituted by.

In the state where the intermediate insulating film is provided as described above, first, the photoresist film 5 is provided on the intermediate insulating film, and the ohmic electrode 2 is formed on the photoresist film 5.
To form a pattern of the openings 6.

Next, as shown in FIG. 4, the polyimide film 4 is selectively wet-etched using the photoresist film 5 as a mask until the silicon nitride film 3 is exposed, and an opening continuous to the opening 6 of the photoresist film 5. Form 7. This wet etching is performed for about 2 minutes by using, for example, ethylenediamine; hydrazine hydride when the thickness of the polyimide film 4 is 1 μm.

In this wet etching,
The polyimide film 4 is slightly side-etched so that the opening 7 becomes slightly larger than the opening 6.

Next, as shown in FIG. 5, the silicon nitride film 3 is selectively dry-etched until the ohmic electrode 2 is exposed by using the photoresist film 5 and the polyimide film 4 as a mask, and an opening 6 is formed in the silicon nitride film 3. , 7 to form a continuous opening 8. This dry etching is performed when the silicon nitride film 3 has a thickness of several thousand angstroms.
Perform for about 30 seconds using gas plasma.

In this dry etching, the silicon nitride film 3 is side-etched slightly and the opening 8 becomes slightly larger than the opening 7.

Next, the photoresist film 5 is removed, a metal (for example, titanium, platinum, gold) is vapor-deposited on the entire surface of the polyimide film 4 and the opening 7, and a new photoresist film is formed on this metal. Form a mask pattern using
By performing electrolytic plating, the second layer wiring 9 is formed.

[0010]

As described above, when the polyimide film 4 and the silicon nitride film 3 are sequentially etched to form the opening 7 and the opening 8, side etching also occurs, and the opening becomes larger. Openings 7, 8
The opening formed by is downward (ie,
This results in an open step shape (toward the ohmic electrode 2).

However, in the conventional manufacturing method as shown in FIG. 6, although the shape of the opening has the above-described step opening downward,
Since the metal is vapor-deposited as it is to form the plating electrode 9 of the second layer, the vapor-deposited metal is cut off at the step portion of the opening, and the plating electrode 9 is disconnected, resulting in a step disconnection. There were cases.

The present invention has been made in view of the above conventional circumstances, and an object of the present invention is to provide a method of manufacturing a semiconductor device capable of reliably preventing the above-mentioned step disconnection with a slight change in the process. To do.

[0013]

A method of manufacturing a semiconductor device according to the present invention which achieves the above object, comprises an intermediate layer formed by stacking a protective film and a polyimide film in layers from the semiconductor substrate side on a semiconductor substrate provided with electrodes. In a method of manufacturing a semiconductor device in which an insulating film is provided and an opening is formed in the intermediate insulating film to connect wiring, a photoresist mask having an opening pattern is provided on the intermediate insulating film and an opening is formed in a polyimide film by etching. A step of forming an opening in the protective film by etching using the photoresist mask and the polyimide film as a mask; and selectively etching the polyimide film again using the photoresist mask to form an opening edge portion of the protective film. On the other hand, a step of retreating the opening edge of the polyimide film to the side, and after removing the photoresist mask, on the intermediate insulating film Characterized by comprising the the steps of providing a plating electrode connected to the electrode.

[0014]

[Function] The intermediate insulating film is etched as in the conventional example,
Openings are sequentially formed in the polyimide film and the protective film of the intermediate insulating film. Then, in the present invention, before forming the second-layer plating electrode, only the polyimide film is selectively etched using the photoresist film used for etching formation of these openings again as a mask, The openings are made larger than the openings of the protective film, and the openings formed by combining these openings are shaped to open upward. Then, as in the conventional example, after removing the photoresist film,
A second-layer plating electrode connected to the electrode on the semiconductor substrate through the opening is formed on the intermediate insulating film.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The description of the same steps as those in the related art will be omitted, and the same reference numerals will be given to the same portions as those in the related art.

In this embodiment, after the target semiconductor device is brought into the state shown in FIG. 5 by the above-mentioned conventional manufacturing method,
It has one additional process. That is, as shown in FIG. 5, the polyimide film 4 and the silicon nitride film 3 are selectively etched to form the openings 7 and 8, and then metal deposition for forming a second-layer plating electrode is performed. Prior to this, selective etching of the polyimide film 4 is performed again.

The polyimide film 4 is again etched by using the photoresist film 5 previously used for etching the openings 7 and 8 as a mask as it is, as shown in FIG. Only the wet etching is selectively performed. This wet etching is performed for about 90 seconds (about 3/4 of the step shown in FIG. 2) using, for example, a mixed solution of ethylenediamine and hydrazine hydride when the thickness of the polyimide film 4 is 1 μm.

As a result, the wall surface of the opening 7 of the polyimide film 4 is side-etched, and the opening 7 becomes larger than the opening 8 of the silicon nitride film 3. Therefore, the opening formed as a whole of the opening 7 and the opening 8 has a shape that opens upward.

After that, the photoresist film 5 is removed in the same manner as in the prior art, and then a metal such as titanium, platinum or gold is vapor-deposited on the entire surface of the polyimide film 4 and the opening 7, and the metal is deposited on the metal. A mask pattern is formed using a new photoresist film, and a second-layer plating electrode 9 connected to the ohmic electrode 2 on the gallium arsenide substrate 1 through the openings 7 and 8 is formed on the polyimide film 4. .

Here, as shown in FIG. 2, since the opening formed in the intermediate insulating film has a step shape that opens upward, the metal for forming the plating electrode 9 is a polyimide film. Since the metal 4 is gently vapor-deposited on the ohmic electrode 2, the vapor-deposited metal will not be cut at the step portion of the opening, and the plating electrode 9 will not be step-broken. Then, a resist pattern having an opening is formed on the ohmic electrode 2 on the plating electrode 9 and selected on the plating electrode 9 by an electrolytic plating method in which a current is applied with the plating electrode 9 as one electrode. The source / drain electrodes are formed by selectively depositing a conductive metal.

In the above embodiments, the semiconductor device using the gallium arsenide substrate has been described as an example, but the present invention is not limited to this, and other types of compound semiconductor substrates, silicon semiconductor substrates, etc. It can be applied to semiconductor devices using various semiconductor substrates. For example, to apply to a multilayer wiring structure of a silicon semiconductor device, a conductive metal layer for the second wiring layer is deposited instead of the plating electrode 9 in the process of FIG. 2 and the conductive metal layer is patterned by photoetching. By doing so, the second wiring layer is formed.

Further, in the above embodiment, an example in which a silicon nitride film is used as a protective film has been described, but the present invention is not limited to this, and a semiconductor using a silicon oxide film (SiO ₂ ) as a protective film. It can also be applied to a device.

[0023]

As described above, according to the present invention, only the polyimide film is formed by using the photoresist film used for forming the opening before forming the second-layer plating electrode on the intermediate insulating film. By selectively etching again, the opening formed in the intermediate insulating film is opened upward, and after that, the plating electrode of the second layer is formed.
Step disconnection of the plating electrode can be reliably prevented. And, this effect can be obtained by only adding a slight step of re-etching only the polyimide film using the photoresist film that was originally used, which causes a drastic change in the manufacturing line and a drastic increase in cost. There is no invitation.

[Brief description of drawings]

FIG. 1 is a sectional view illustrating a method according to an embodiment of the present invention.

FIG. 2 is a sectional view illustrating a method according to an embodiment of the present invention.

FIG. 3 is a sectional view illustrating a method of a conventional example.

FIG. 4 is a cross-sectional view illustrating a method of a conventional example.

FIG. 5 is a cross-sectional view illustrating a method of a conventional example.

FIG. 6 is a cross-sectional view illustrating a method of a conventional example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01L 21/90 B

Claims (1)

[Claims] 1. An intermediate insulating film formed by stacking a protective film and a polyimide film in layers from the semiconductor substrate side on a semiconductor substrate provided with electrodes, and an opening is formed in this intermediate insulating film to connect wiring. In the method of manufacturing a semiconductor device, a step of forming an opening in a polyimide film by etching by providing a photoresist mask having an opening pattern on the intermediate insulating film, and a protective film by etching using the photoresist mask and the polyimide film as a mask. A step of forming an opening, a step of selectively etching the polyimide film again by using the photoresist mask, and a step of laterally retreating the opening edge portion of the polyimide film with respect to the opening edge portion of the protective film, Providing a wiring connected to the electrode on the intermediate insulating film after removing the photoresist mask. Manufacturing method of semiconductor device.